The invention relates to a Method for reception of DVB-H signals wherein a MPEG transport stream (MPEG-TS) is grouped into packets belonging to a certain IP data stream and forming bursts in time slices, the MPEG-TS is modulated into OFDM symbols, these symbols are grouped in frames, the frames themselves are grouped in superframes and symbols, frames and superframes are provided with numbers. The invention is basing on the assumption that a transmitter does not change the transmission parameters (FFT mode, guard interval, code rate, modulation format) between successive bursts. A receiver is notified about a relative time from a first burst to transmission of the next burst and the receiver is switched off between the first and the next burst.
The invention further relates to a DVB-H receiver consisting of a RF module, a DVB-T baseband receiver, an analog-to-digital converter, a clock and a protocol processor.
DVB-H is the most promising standard for bringing digital television (TV) to mobile handheld devices. DVB-H is based on the existing DVB-T standard and the IP datacasting mode thereof, where the benefit for mobile devices comes from intelligently grouping MPEG transport stream (TS) packets (the interface to the physical layer).
Conventional DVB-T receivers are designed for continuous reception of DVB-T streams. A relatively long time can be tolerated for signal acquisition, i.e.,
(1) identifying the presence of a DVB-T signal, then
(2) identifying the mode (2 k or 8 k FFT size and the duration of the guard interval),
(3) achieving time and frequency synchronizations,
(4) achieving frame synchronization and obtaining a first estimate of the channel.
Only after full synchronization (steps 1-4) is achieved, the demodulation of the received signal can start.
The DVB-T frame is organized as follows:
68 symbols form a so called frame. The symbols are numbered increasingly starting with the beginning of a frame.
4 frames are grouped to form a super frame. The frame number is signaled in the transmission parameter signaling (TPS) symbols which are multiplexed into the OFDM symbols.
Frame synchronization is important for several reasons.
The interleaver patterns change from even to odd symbol numbers.
The positions of the scattered pilots depend on the symbol number modulo 4. The scattered pilot positions also affect the location of the data carriers in the OFDM symbol.
The DVB-T standard guarantees an integer multiple of MPEG transport stream packets (TS) to be contained in a super frame. For the channel decoding logic, it is essential that the received data are aligned accordingly, i.e., the MPEG-TS packet boundaries are known.
The conventional DVB-T receiver first establishes frame synchronization, then waits for the beginning of a super frame, and then starts pushing demodulated data through the channel decoding logic.